The Scottish Labour Party was the most successful party in Scottish elections from 1959 to 2007. Like the wider UK Labour Party, they are centre-left and they promote British unionism. They first overtook the Conservatives as Scotland's largest party at the 1959 general election. In 1997, the UK Labour Party under Tony Blair offered Scotland a referendum on devolution which was passed with around 74% of the electorate in favour. From 1999 to 2007, they were in power in the Scottish Parliament through a coalition with the Liberal Democrats. From 2008-2011, the party was led by Iain Gray in the Scottish Parliament, who announced his resignation after the party's defeat at the 2011 Scottish election. Johann Lamont became leader in 2011 and resigned in 2014 after an internal dispute within the party. They control just one Scottish seat in the House of Commons after a landslide defeat in the 2015 General Election to the SNP. They also have 37 seats in the Scottish Parliament and have two MEPs. They are currently led by Kezia Dugdale MSP, following Jim Murphy's resignation after the 2015 General Election.

UKIP Scotland, the Scottish section of the eurosceptic UK Independence Party, has contested many Scottish elections for the Westminster Parliament and the Scottish Parliament, and in 2014 it won one of Scotland's six seats in the European Parliament, gaining 10.5% of the Scottish vote, coming fourth. Its Scottish MEP is David Coburn.

The Scottish Socialist Party (SSP) was founded in 1998 by Tommy Sheridan and achieved 6 seats in the Scottish Parliament in 2003. They are left-wing, and campaign for Scottish independence, the abolition of council tax, Free school meals, free public transport and an end to the Afghan War. A party split in 2006 caused party leader Tommy Sheridan to establish Solidarity, whose policies were quite similar to the SSP. Both the SSP and Solidarity won no seats at either the 2007 or 2011 Scottish parliamentary elections.